That is a fair assumption. In the experiment, it is. The only reason I can't use a simple diffusion equation is that constant flow. This is actually only a first step though, I need to find how much of the solute gets in the smaller tube when there is a non-constant flow. We can still assume...
I have two cylindrical tubes connected at a 90 degree junction. One tube has a constant flow of a laminar fluid going through it and the fluid is saturated by a soluble particulate with a known concentration. The other tube has a much smaller radius, initially has no particles and is closed at...